Method and system for monitoring instantaneous behavior of a tire in a rolling condition

ABSTRACT

A method for monitoring instantaneous behavior of a tire in a rolling condition includes acquiring and storing at least one reference curve representing an acceleration profile of at least one specified point of the tire as a function of its position during at least one portion of a revolution of the tire; continuously acquiring signals of acceleration of the at least one point; deriving from the signals of acceleration at least one cyclic curve of acceleration of the at least one point; comparing the at least one cyclic curve with the at least one reference curve; and emitting a signal depending on the comparison that indicates the instantaneous behavior of the tire. The at least one reference curve represents the acceleration profile in at least two directions, including two or more of a centripetal direction, a tangential direction, and a lateral direction. A related system and tire are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national-phase entry under 35 U.S.C. § 371 fromInternational Application No. PCT/EP02/03498, filed Mar. 28, 2002, inthe European Patent Office, the content of which is relied upon andincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and system for monitoring theinstantaneous behaviour and interaction with the road of a tire duringthe running of a motor vehicle equipped with tires.

2. Description of the Related Art

A tire of a motor vehicle, when rolling on a road surface, is subject toa vertical load and to tangential and transverse external forces, whichare generated in the various manoeuvres, such as braking, acceleration,cornering, straight line running etc.

During each manoeuvre, any point on the tire rolling in steady state andin transitory conditions carries out a movement, which can berepresented by displacements in the three spatial directions, for eachcycle of the revolution of the tyre. The movement of any points havecharacteristics which are typical of the position of each particularpoint of the structure, of the external profile of the tyre, of theconditions of use (speed, load and pressure), of the conditions of thesurface on which the tyre rolls, and of the external forces to which thetyre is subjected in the manoeuvres of braking, acceleration, cornering,etc.

The patent application EP887211 describes a tire monitoring system for atire on a vehicle comprising: a sensor device operatively arranged withrespect to the tire to create an electrical pulse during the footprintpass corresponding to a deformation of the tire; means for calculating aratio of the duration of said electrical pulse to the duration of onetire revolution; means for transmitting said ratio to an evaluating unitplaced in the vehicle. Said sensor device is placed within the treadarea of said tire in order that said electrical pulse presents a firstmaximum at the entrance and a second maximum at the leaving of saidfootprint pass.

The patent application WO0136241 in the name of the same applicant ofpresent application describes a method for monitoring the instantaneousbehaviour of a tyre during the running of a motor vehicle, comprisingthe steps of

-   acquiring and storing, at least temporarily, at least one basic    reference curve which represents the variation of the displacement    of at least one specified point of the said tyre in at least one    spatial direction, as a function of the spatial position of the    point, in at least one portion of a revolution of the tyre,-   continuously acquiring signals of the position in space of the    specified point of the tyre,-   deriving from the position signals at least one cyclic curve of    operating displacement of the point in the spatial direction, as a    function of the spatial position of the point, in at least one    portion of a revolution of the tyre,-   continuously comparing the said curve of operating displacement with    the said basic reference curve of displacement, and-   emitting a signal depending on the comparison and indicating the    instantaneous behaviour of the tyre.

The patent U.S. Pat. No. 6,204,758 describes a tire monitor for use in aremote tire monitor system including an accelerometer for detectingacceleration of the tire monitor. Location (relative to vehicle)information for the tire monitor is determined in response to theacceleration. In this manner, tire location (relative to the vehicle)information is determined automatically to allow the system to displaytire characteristic data such as air pressure in conjunction with tirelocation (front right, front left).

SUMMARY OF THE INVENTION

The Applicant has observed that the deformations of a tire in a rollingcondition occur in a plurality of directions with respect to a localreference frame. Said local reference frame is a reference on which thedeformations are detected (e.g. an orthogonal axes system or a polaraxes system). For example, a deformation of the tire due to a loadvariation on said tire is substantially a deformation in a centripetaldirection, which is a radial direction of said tire. During a brakingcondition the deformations of the tire are mainly in a tangentialdirection, which is a direction tangential to the circumference of saidtire and during a cornering condition the deformations of the tire aremainly in a lateral direction, which is a direction orthogonal to bothsaid lateral and centripetal directions.

The Applicant has observed that the accelerations and their variation ina predetermined temporal interval of specific points of a tire, withrespect to said local reference frame, are in relationship with saiddeformations of the tire, which are generated from the interactionsbetween the tire in motion and the ground.

The Applicant has perceived that to monitoring the deformations of atire in a rolling condition an acceleration profile in at least twodirections of said local reference frame should be detect.

Moreover, the Applicant has tackled the problem of choosingcharacteristic points of the tire, on which measuring said accelerationprofile as a function of the position of said points, having arelationship each other with respect to the global behaviour of thetire. Moreover, the applicant has tackled the problem of analysingmeasured curves of accelerations for said specific points for at least acomplete rolling of the tire.

Moreover, the Applicant has observed that each of said specific pointshas a specific behaviour with respect to the interactions between thetire and the road.

The Applicant has found that, to monitor the deformations of a tire, theacceleration of a first characteristic point and the acceleration of asecond characteristic point may be compared. In general to obtain aglobal indication of the behaviour of a tire more than onecharacteristic point of the tire has to be monitored. For eachmanoeuvre, which has to be monitored, there are characteristic points,which have a more direct correlation between said accelerations and thedeformations of the tire than other points of the tire itself. Thedeformations of said chosen points are in relationship with theinstantaneous behaviour of the tire and interaction between the road andthe tire itself.

Moreover, the accelerations of-a specific point on a rolling tyre, whichis subject to specific forces, has the same basic shape (basic curve)for each revolution of the tyre, while it varies as to the position andamplitude of the peaks, and/or the start and end of each peak, and therelative maximum and/or minimum, and/or a “slope” of particular portionsof the curve.

The Applicant has found that, to monitor the behaviour of a tire duringthe above-cited manoeuvres of a vehicle in motion, predetermined portionof said curves may be monitored. Said curves assume significant valuesin proximity (before and after) the passage of the monitored points intothe physical contact between the tire and the road. Preferably,monitored portions of said curves may be associated with specificdeformations corresponding to specific phenomena (e.g. aquaplaningphenomenon, a locked wheel etc . . . )

A first aspect of present invention is referred to a method formonitoring the instantaneous behaviour of a tyre in a rolling condition,comprising the steps of

-   a) acquiring and storing, at least temporarily, at least one    reference curve which represents the acceleration profile of at    least one specified point of the said tyre in at least two    directions selected from a centripetal, a tangential and a lateral    directions as a function of the position of the said point, in at    least one portion of a revolution of the said tyre,-   b) continuously acquiring signals of the acceleration in said at    least two directions of said at least one point of the said tyre, in    at least one portion of a revolution of the said tyre,-   c) deriving from the said signals at least one cyclic curve of    acceleration profile of the said at least one point in at least the    said portion of a revolution of the said tyre,-   d) comparing said at least one cyclic curve with the said at least    one reference curve, and-   e) emitting a signal depending on the said comparison, the said    signal indicating the said instantaneous behaviour of the said tyre.

Preferably, said step of comparing comprises comparing said at least onereference curve and said at least one cyclic curve point by point for anentire revolution of the tire.

Preferably, said step of comparing comprises comparing a reference curvederived from a first point on the tire and a cyclic curve derived from asecond point on the tire.

Preferably, said first point is located on the liner surface along theequatorial plane of the tire and said second point is located on theliner surface on a shoulder of said tire, said first and second pointsbeing located along the same meridian plane of the tire.

Preferably, said first point is located on the liner surface along theequatorial plane of the tire on a left shoulder of said tire and saidsecond point is located on the liner surface on a right shoulder of saidtire, said first and second points being located along the same meridianplane of the tire.

Preferably, said first point is located on the liner surface along theequatorial plane of the tire and the second point is located on theliner surface along the equatorial plane distant from said first pointfor a predetermined arc.

Preferably, said step of comparing comprises comparing characteristicpeaks of said at least one reference curve with correspondentscharacteristic peaks of said at least one cyclic curve.

Preferably, said step of comparing comprises comparing a portion of thearea under said at least one reference curve with the correspondentportion of the area under said at least one cyclic curve.

A further aspect of present invention is referred to a system formonitoring the instantaneous behaviour of a tyre in a rolling conditioncomprising:

-   i. at least one memory element for acquiring and storing, at least    temporarily, at least one reference curve which represents the    acceleration profile of at least one specified point of the said    tyre in at least two directions selected from a centripetal, a    tangential and a lateral directions in at least one portion of a    revolution of the tyre,-   ii. at least one sensor associated with the said at least one    specified point of the said tyre, capable of emitting, over a period    of time, signals of the acceleration in said directions of the said    point,-   iii. a receiving device capable of continuously acquiring the said    signals of the acceleration of the said at least one point of the    said tyre, in at least the said portion of a revolution of the said    tyre, and-   iv. an elaboration unit incorporating a program capable of    determining from the said signals of acceleration at least one    cyclic curve of acceleration of the said at least one point in the    said directions in at least the said portion of a revolution of the    said tyre,-   v. said elaboration unit being capable of continuously comparing    said at least one of cyclic curves of acceleration with said at    least one stored reference curve,-   vi. said elaboration unit being additionally capable of emitting a    signal depending on the said comparison, the said signal indicating    the said instantaneous behaviour of the said tyre.

Preferably, a first sensor is located on the liner surface along theequatorial plane of the tire and a second sensor is located on the linersurface on a shoulder of said tire, said first and second sensors beinglocated along the same meridian plane of the tire.

Preferably, a first sensor is located on the liner surface along theequatorial plane of the tire on a left shoulder of said tire and asecond sensor is located on the liner surface on a right shoulder ofsaid tire, said first and second sensors being located along the samemeridian plane of the tire.

Alternatively, a first sensor is located on the liner surface along theequatorial plane of the tire and a second sensor is located on the linersurface along the equatorial plane distant from said first sensor for apredetermined arc.

Preferably, said system further comprising a third sensor located on theliner surface along the equatorial plane of the tire distant from saidsecond sensor for a predetermined arc.

Preferably, said first and second and third sensors are equidistant eachother.

Preferably, a third sensor is located on the opposite shoulder of saidsecond sensor along the same meridian plane of said first and secondsensor.

Preferably, said system further comprises a speed sensor of said tire.

Preferably, said system further comprises a pressure sensor of saidtire.

A further aspect of present invention is referred to a pneumatic tirecomprising at least one sensor associated with at least one specifiedpoint of said tire, capable of emitting, over a period of time, asignal, which represents the acceleration profile of said at least onespecified point, in at least two directions selected from a centripetal,a tangential and a lateral directions as a function of the position ofthe said point, in at least one portion of a revolution of the saidtire.

BRIEF DESCRIPTION OF THE DRAWINGS

Characteristics and advantages of the invention will now be illustratedwith reference to one embodiment represented in the attached figures, inwhich:

FIG. 1 shows schematically, in a section view, a rolling tyre having asensor disposed on its internal surface, according to an embodiment ofthe present invention;

FIG. 2 shows schematically, in a side view, a rolling tyre having threesensors disposed on the liner internal surface, according to a furtherembodiment of the present invention;

FIG. 3 shows schematically, in a side view, a rolling tyre having threesensors disposed on the liner internal surface, according to a furtherembodiment of the present invention;

FIG. 4 shows a diagram block of an example of a system to monitoring thebehaviour of a vehicle according with present invention;

FIG. 5 shows three graphs respectively of the centripetal, tangentialand lateral acceleration of a specific point of a tire which ismonitored by means of the sensor of FIG. 1;

FIG. 6 shows a further graph of the centripetal acceleration of specificpoints of a tire which is monitored by means of the sensors of FIG. 1 infree rolling at different speeds (same load);

FIG. 7 shows a further graph of the centripetal acceleration of specificpoints of a tire, which is monitored by means of the sensors of FIG. 3;

FIG. 8 shows a further graph of the centripetal acceleration of specificpoints of a tire, which is monitored by means of the sensors of FIG. 3in free rolling and in cornering condition.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The tyre of FIG. 1 consists of an internally hollow toroidal structureformed by a plurality of components, and primarily by a textile ormetallic carcass, having two beads and each formed along an innercircumferential edge of the carcass for securing the tyre to acorresponding supporting rim. The said carcass comprises at least onepair of annular reinforcing cores, called bead wires, which are insertedin the said beads.

The carcass comprises a supporting structure formed by at least areinforcing ply which includes textile or metallic cords, extendingaxially from one bead to the other according to a toroidal profile, andwhich has each of its ends associated with a corresponding bead wire.

In tyres of the type known as “centripetal”, the aforesaid cords lieessentially in planes containing the axis of rotation of the tyre.

On the crown of this carcass there is placed an annular structure, knownas the belt structure, normally consisting of one or more strips ofrubberized fabric, wound on top of each other to form what is called a“belt package”, and a tread made from elastomeric material, wound aroundthe belt package, and stamped with a relief pattern for the rollingcontact of the tyre with the road. Two sidewalls, made from elastomericmaterial, each extending outwards in the centripetal direction from theouter edge of the corresponding bead, are also placed on the carcass, inlateral axially opposed positions.

In tyres of the type known as “tubeless”, the inner surface of thecarcass is normally covered with a “liner” layer, in other words one ormore layers of airtight elastomeric material. Finally, the carcass maycomprise other known elements, such as edges, strips and fillers,according to the specific design of the tyre.

It should be specified that, for purposes of the present description,the term “elastomeric material” indicates a material obtained bycrosslinking a rubber composition comprising at least an elastomericpolymer having at least a filler dispersed therein and usuallyconventional additives such as curatives, processing aids, etc . . . .

The combination of all these elements determines the mechanicalcharacteristics of elasticity, rigidity and resistance to deformation ofthe tyre, which constitute the connection between the system of forcesapplied to the tyre and the extent of the corresponding deformationswhich it undergoes.

One aspect of the present invention relates to the measurement of thevariations of the acceleration of at least a specified point of a tire,in a predetermined temporal interval with respect to a local referenceframe. Said local reference frame is a reference on which theacceleration values and directions are measured (i.e. a orthogonal axessystem or a polar axes system).

Said variations are in relationship with the interactions between thetire in motion and the ground and are in relationship with thedeformations of the tire itself during motion.

To this purpose at least a sensor, which is able to measure saidacceleration, is associated to the tire.

Preferably, more than one sensor is associated to the tire and eachsensor is disposed in a predetermined position of the tire. Preferably,said sensors are disposed on the internal surface of the tire andpreferably in contact with said liner layer where such liner is present.Alternatively, one or more of said sensors may be inserted into theliner layer or into the tread band layer or into the carcass of the tireduring the manufacturing process, i.e. into the beads. Moreover, thesystem of the present invention may provide a further sensor, which isable to measure the displacement of said point with respect to a localreference frame (i.e. optic).

In the embodiment of FIG. 1 a sensor 2 is associated to the tyre 1 andit is preferably disposed on the internal surface of the tire, inparticular on the liner surface 111. More preferably, said sensor isdisposed along the equatorial plan of said tire. For example said sensoris associated to said liner surface by means of a glue or a siliconsealant or an elastomeric compound liner compatible or similar.

Alternatively, said sensor is inserted into the liner layer or into thetread band layer, or inside the carcass or inside the bead during a tiremanufacturing process.

Preferably, the sensors of present invention are accelerometers, whichare able to measure the accelerations of the point of the tire on whichthey are associated with respect to a local reference frame.

In particular, in FIG. 1 the sensor 2 is able to measure theacceleration profile of the point P with respect to at least twodirections selected from the x, y and z local axes. Said x, y and zlocal axes represent three direction that for the purpose of the presentdescription are named respectively:

-   centripetal direction z which is a radial direction of said tire,-   tangential direction y which is a direction tangential to the    circumference of said tire,-   lateral direction x which is a direction orthogonal to both said    centripetal and tangential directions.

Then, said sensor 2 is able to measure the acceleration profile of thepoint P with respect to at least two directions selected from saidcentripetal direction, said tangential direction and said lateraldirection.

In FIG. 2 a further embodiment of the present invention is shown. Insuch figure three sensors 21, 22, and 23 are associated to a tire 1.Preferably, the sensors are disposed in points on the inner surface ofthe tire. More preferably, said sensors are disposed in a centralposition, along an equatorial plane E of said tire and said sensors areequidistant each other. In particular said sensors are located in acircumferential position spaced one from the other of a predeterminedarc.

This disposition gives more accuracy, reliability to know info in fasterway in order to better monitor the entire wheel turn. For example,during a revolution of the tire it is possible to monitoring at the sametime the acceleration during the footprint pass with a first sensor andthe acceleration of a point located before the footprint pass with asecond sensor and the acceleration of a point located after thefootprint pass with a third sensor.

In FIG. 3 a further embodiment of the present invention is shown. Insuch figure three sensors 21′, 22′ and 23′ are associated to a tire 1.

Preferably, a first sensor 21′ is disposed on the internal surface ofthe liner 111 in a central position along the equatorial plane E of thetire. Preferably the other two sensors 22′ and 23′ are disposed on thesame surface each of them positioned between the central line and saidsidewalls of the tire (hereinbelow they are named left shoulder sensor22′ and right shoulder sensor 23′ respectively). Preferably, saidsensors 21′, 22′ and 23′ are disposed along the same meridian plane M ofthe tire. Said disposition allows to monitor the general behavior of thefull interaction area between the tire and the road; for instance whenthe tyre is cornering the signals derived from the two sensors 23′ and22′ change relative to each other. Other maneuvers can be detected bycomparing the signal of the sensor 21′, 22′, 23′, (e.g. in a case of anaquaplaning phenomenon).

It has to be noted that said sensors may be disposed in other points ofsaid tire in a way to measure the variations of acceleration of saidpoints and in a way to compare the signals derived from differentsensors, if said points are key points able to give information on thebehavior of said tire in motion.

Alternatively, said sensors may be associated with points of the tirelocated at tread level, at carcass sidewall level, or at liner level, orbead level, or with intermediate points. Moreover one of said sensorsmay be located on the rim of the wheel; in this case a comparisonbetween the signal of the rim sensor and another signals derived form asensor located on a liner surface may give an indication of the relativemovement between the rim and the tire for example during a brakingmanoeuvre.

In FIG. 4 is shown an example of a system to monitoring the behavior ofa vehicle. In particular, FIG. 4 shows the sensors 2 or 21, 22, 23 or21′, 22′ and 23′, a receiving device 6 associated with said sensors andan elaboration unit 7 connected to said receiving device 6. Theelaboration unit 7 comprises, for example a volatile storage element 7a, a permanent storage element 7 b and processor 7 c. The sensor aremounted, as stated above, at specified points of the tire, while thereceiving device 6 and the elaboration unit 7 are mounted preferably onthe vehicle. For example said receiving device and said elaboration unitmay be part of an on-board computer of the vehicle. The receiving device6 is, for example, an electromagnetic radio frequency receiver. Saidsensors are preferably provided with a piezoelectric device or apiezoresitive device or with a silica based device in a way to generatea signal correspondent to the acceleration of the point on which theyare associated. Said signal could be transmitted to said receiver 6 bymeans of radio wave more preferably by means of high frequency radiowave.

The inventors have observed that by measuring the acceleration ofcharacteristic points of the carcass, during its travel, it is possibleto verify whether the tyre is being subjected to braking, acceleration,or cornering, or knowing the friction available between the tire itselfand the road, or when the tire is close to aquaplaning and whether ornot it is in an area of instability.

In FIG. 5 is shown three experimental graphs respectively ofcentripetal, tangential and lateral acceleration of a tire with a sizeof 205/55/R16 rolling at 80 Km/h over a drum with a diameter of 1.7meter, measured from the sensor of FIG. 1. Said local reference frame,labeled with x, y, z, is shown in right upper corner of the figure.

In FIG. 6 a further graph of the centripetal acceleration of the sametire of the FIG. 5 at different speeds and at the same load are shown.This figure shows that the curves at different speeds have the sameshape but different amplitude, in particular for the peak-to-peakvalues.

In FIG. 7 a further graph of the acceleration of the same tire of FIG. 5measured from the sensors of FIG. 3 is shown. In particular, in FIG. 7two curves are shown. A first curve S1 refers to the central sensor 21′of FIG. 3, the second curve S2 refers to the left shoulder sensor 22′ ofFIG. 3. The conditions of motion of the tire are 4500 N of load, 2.2 barof tire pressure, 120 Km/h of speed.

In FIG. 8 a further graph of the acceleration of the same tire of FIG. 5measured from the sensors of FIG. 3 is shown. In particular, in FIG. 8two curves are shown. A first curve S1′ refers to the right shouldersensor 23′ of FIG. 3, the second curve S2′ refers to the left shouldersensor 22′ of FIG. 3. Said tire is in a left cornering condition of 3°and the other conditions (speed and load) are the same of FIG. 7.

The applicant has noted that the sensor 23′ (right shoulder), in aregion that contains the footprint area of the tire, measures anacceleration which is greater than the acceleration measured from thesensor 22′ (left shoulder). This is due to the deformation of the tireduring said cornering condition. By monitoring the difference betweenthe accelerations measured from said two sensors the system of thepresent invention is able to detect a critique condition during acornering manoeuvre. For example said critique condition may be detectedby comparing said difference of accelerations with a predeterminedthreshold value or by comparing (point to point) a curve monitored by ashoulder sensor with a reference curve stored into one of said memoryelements.

According to present invention specified reference curves may be storedin said volatile storage element 7 a or in the permanent storage element7 b of the elaboration unit 7, in a temporary or permanent wayrespectively.

Said reference curves may be during a setup phase of the system and maybe generated by each of the sensors of the system.

For example, the basic reference curves, which represent, respectively,the cyclic variation, in one revolution of the tire, of theaccelerations of predetermined points of the tire may be stored in thestorage elements 7 a or 7 b. Moreover more than one reference curve maybe stored in both said storage elements 7 a and 7 b.

The receiving device 6 receives the signals emitted by the sensorsduring the motion of the tire and sends them to the elaboration unit 7,which is preferably programmed to process them. Said signals arecorrespondent to curves of the signals amplitude in a predetermined timeinterval.

Each cyclic curve of centripetal or tangential or lateral accelerationis compared in the elaboration unit 7 with said basic reference curvesstored, and the information on the state of instantaneous behavior ofthe tyre and/or on the instantaneous adhesion between the tyre and theroad is obtained from the comparisons.

Example of comparisons between a basic reference curve and a monitoredcyclic curve are the following:

-   comparision of two curves completely point by point for a entire    revolution of a tire, or-   comparision of some characteristic peaks of one reference curve with    correspondents characteristic peaks of one monitored cyclic curve,    or-   comparision of the entire area under one reference curve with the    correspondent entire area under one correspondent monitored cyclic    curve, or-   comparision of a temporal portion of the area under one reference    curve with the correspondent temporal portion of the area under one    correspondent monitored cyclic curve, or-   comparision of a predetermined number of monitored cyclic curves    with a reference curve in a way to obtain a time history of the    monitored points of the tire.

Other information may be obtained by comparing signals derived fromsensors associated to different tires of a vehicle. For example tomonitoring a breaking of a vehicle a comparison between signal derivedfrom the front tires and signals derived from sensors of the rear tiresof the vehicle may be realized. Another example of a comparison betweensignals derived from sensors located in different tires of the vehiclemay be accomplished during a cornering condition, in which thedifference between signals derived from a tire on one side of thevehicle may be compared with signals derived from a tire on the otherside of the vehicle.

Moreover, according to the present invention more than one sensor on thesame tire may be associated. In this case, many comparisons of thesignals derived from two different sensors of the same tire may beobtained (i.e. in the above cornering condition).

Preferably, the basic reference curves are acquired during the runningof the motor vehicle on the road, in the course of each revolution ofthe tyre. The basic reference curves (or the values of thecharacteristics points) are stored temporarily to carry out thecomparison with the current cyclic operating curves, acquired in atleast a successive revolution of the said tyre. For example, the cyclicoperating curve acquired in a revolution of the tyre is compared with abasic reference curve acquired in the preceding revolution of the tyrein the i-th preceding revolution.

Alternatively, said curves (reference curves and cyclic curves) may bestored in a memory element inside of each sensor. In such case, anelaboration unit is located inside of each sensor and theabove-described comparison step of the acceleration signal is madeinside of each sensor.

In order to avoid accidental mistakes in the sensor signal generation ortransmission, advantageously, specified pairs or triplets ofacceleration of specific points emitted by two or more sensorsassociated with two or more specified points of the tyre could be alsoprocessed in the elaboration unit 7.

The information obtained from said comparisons can be used subsequentlyto set control actions of mechanisms of the motor vehicle, for exampleregulation of the brake system (longitudinal behaviour and/or lateralone), or active suspension, or to give info concerning the status of thetyre (wearing situation, adhesion coefficient available, etc) andsimilar.

Advantageously, the accelerations of the monitored points may beintegrated with other information of the vehicle, for example the speedof the vehicle and/or the tire pressure. Said other information may bemeasured by other sensors.

The Applicant has observed from the curves of graphs of FIG. 5-9 that,in a complete revolution of the tire, there are portions of said curves,which assume more significant value than other portions of said curves.For example, said curves assume significant values in proximity (beforeand after) the passage of the monitored point into the physical contactbetween the tire and the road: see FIG. 6 as example.

This means that the data (i.e. accelerations) derived from the sensorlocated in a defined point of the tire can give important info (i.e.concerning the way to approach the road interaction and the way to leavethis interaction) not only when this point is close the contact area.There are other regions in which said signals derived from the sensorsassume critical values, for example in the opposite side of thefootprint region.

The main changes during the tire life (e.g. wear or structuralmodification) can be in fact found also comparing the different curvesgenerated by the sensor signals in this region at different times (i.e.montly).

1. A method for monitoring instantaneous behavior of a tire in a rollingcondition, comprising: acquiring and storing, at least temporarily, atleast one reference curve representing an acceleration profile of atleast one specified point of the tire during at least one portion of arevolution of the tire; continuously acquiring signals of accelerationof the at least one point during the at least one portion of arevolution; deriving from the signals of acceleration at least onecyclic curve of acceleration of the at least one point during the atleast one portion of a revolution; comparing the at least one cycliccurve with the at least one reference curve; and emitting a signaldepending on the comparison; wherein the at least one reference curverepresents the acceleration profile of the at least one point in atleast two directions, wherein the directions comprise two or more of acentripetal direction, a tangential direction, and a lateral direction,wherein the signals of acceleration of the at least one point in the atleast two directions are continuously acquired, and wherein the emittedsignal indicates the instantaneous behavior of the tire.
 2. The methodof claim 1, wherein comparing the at least one cyclic curve with the atleast one reference curve comprises: comparing the at least one cycliccurve with the at least one reference curve point-by-point for an entirerevolution of the tire.
 3. The method of claim 1, wherein comparing theat least one cyclic curve with the at least one reference curvecomprises: comparing a cyclic curve derived from a first point on thetire with a reference curve derived from a second point on the tire. 4.The method of claim 3, wherein the first point is located on a linersurface along an equatorial plane of the tire, wherein the second pointis located on the liner surface on a shoulder of the tire, and whereinthe first and second points are located along a same meridian plane ofthe tire.
 5. The method of claim 3, wherein the first point is locatedon a liner surface on a first shoulder of the tire, wherein the secondpoint is located on the liner surface on an opposite shoulder of thetire, and wherein the first and second points are located along a samemeridian plane of the tire.
 6. The method of claim 3, wherein the firstpoint is located on a liner surface along an equatorial plane of thetire, and wherein the second point is located on the liner surface alongthe equatorial plane of the tire, and wherein the first point is apredetermined arc distance from the second point.
 7. The method of claim1, wherein comparing the at least one cyclic curve with the at least onereference curve comprises: comparing characteristic peaks of the atleast one cyclic curve with corresponding characteristic peaks of the atleast one reference curve.
 8. The method of claim 1, wherein comparingthe at least one cyclic curve with the at least one reference curvecomprises: comparing a portion of an area under the at least one cycliccurve with a corresponding portion of an area under the at least onereference curve.
 9. A system for monitoring instantaneous behavior of atire in a rolling condition, comprising: at least one memory element foracquiring and storing, at least temporarily, at least one referencecurve representing an acceleration profile of at least one specifiedpoint of the tire during at least one portion of a revolution of thetire; at least one sensor associated with the at least one point foremitting, over a period of time, signals of acceleration of the at leastone point; a receiving device for continuously acquiring the signals ofacceleration of the at least one point during the at least one portionof a revolution; and an elaboration unit incorporating a program fordetermining from the signals of acceleration at least one cyclic curveof acceleration of the at least one point during the at least oneportion of a revolution; wherein the elaboration unit continuouslycompares the at least one cyclic curve with the at least one referencecurve, wherein the elaboration unit emits a signal depending on thecomparison, wherein the at least one reference curve represents theacceleration profile of the at least one point in at least twodirections, wherein the directions comprise two or more of a centripetaldirection, a tangential direction, and a lateral direction, wherein thesignals of acceleration of the at least one point in the at least twodirections are emitted, and wherein the emitted signal depending on thecomparison indicates the instantaneous behavior of the tire.
 10. Thesystem of claim 9, wherein a first sensor is located on a liner surfacealong an equatorial plane of the tire, wherein a second sensor islocated on the liner surface on a shoulder of the tire, and wherein thefirst and second sensors are located along a same meridian plane of thetire.
 11. The system of claim 9, wherein a first sensor is located on aliner surface on a first shoulder of the tire, wherein a second sensoris located on the liner surface on an opposite shoulder of the tire, andwherein the first and second sensors are located along a same meridianplane of the tire.
 12. The system of claim 9, wherein a first sensor islocated on a liner surface along an equatorial plane of the tire, andwherein a second sensor is located on the liner surface along theequatorial plane of the tire, and wherein the first sensor is a firstpredetermined arc distance from the second sensor.
 13. The system ofclaim 12, further comprising: a third sensor located on the linersurface along the equatorial plane of the tire; wherein the secondsensor is a second predetermined arc distance from the third sensor. 14.The system of claim 13, wherein the first, second, and third sensors areequidistant from each other.
 15. The system of claim 10, furthercomprising: a third sensor located on the liner surface on an oppositeshoulder of the tire; wherein the first, second, and third sensors arelocated along the same meridian plane of the tire.
 16. The system ofclaim 9, further comprising a speed sensor of the tire.
 17. The systemof claim 9, further comprising a pressure sensor of the tire.
 18. Apneumatic tire, comprising: at least one sensor associated with at leastone specified point of the tire; wherein the at least one sensor emits,over a period of time, a signal representing an acceleration profile ofthe at least one point of the tire during at least one portion of arevolution of the tire, wherein the signal represents the accelerationprofile in at least two directions, and wherein the directions comprisetwo or more of a centripetal direction, a tangential direction, and alateral direction.
 19. The method of claim 1, wherein the at least onereference curve represents an acceleration profile of at least onespecified point of the tire as a function of position of the at leastone point during at least one portion of a revolution of the tire. 20.The pneumatic tire of claim 18, wherein the signal represents anacceleration profile of the at least one point of the tire as a functionof position of the at least one point during at least one portion of arevolution of the tire.
 21. The pneumatic tire of claim 18, wherein afirst sensor is located on a liner surface along an equatorial plane ofthe tire, wherein a second sensor is located on the liner surface on ashoulder of the tire, and wherein the first and second sensors arelocated along a same meridian plane of the tire.
 22. The pneumatic tireof claim 18, wherein a first sensor is located on a liner surface on afirst shoulder of the tire wherein a second sensor is located on theliner surface on an opposite shoulder of the tire, and wherein the firstand second sensors are located along a same meridian plane of the tire.23. The pneumatic tire of claim 18, wherein a first sensor is located ona liner surface along an equatorial plane of the tire, wherein a secondsensor is located on the liner surface along the equatorial plane of thetire, and wherein the first sensor is a first predetermined arc distancefrom the second sensor.
 24. The pneumatic tire of claim 23, furthercomprising a third sensor located on the liner surface along theequatorial plane of the tire, wherein the second sensor is a secondpredetermined arc distance from the third sensor.
 25. The pneumatic tireof claim 24, wherein the first, second, and third sensors areequidistant from one another.
 26. The pneumatic tire of claim 21,further comprising a third sensor located on the liner surface on anopposite shoulder of the tire, wherein the first, second, and thirdsensors are located along the same meridian plane of the tire.
 27. Thepneumatic tire of claim 18, further comprising a sensor configured tooutput a signal indicative tire speed.
 28. The tire of claim 18, furthercomprising a sensor configured to output a signal indicative of tirepressure.